Your amp certainly wasn't set up with a solid
state rectifier when it was brand new! You can
bet that the original power transformer had
blown and the owner couldn't find an exact
replacement, so he used a transformer from
a Bassman head instead.

There's no harm leaving the amp set up this
way, but if you're looking to get the original
tone (and dynamics, esp. at higher volumes),
I recommend getting the proper replacement.
Mojo Musical Supply sells one under their own
name that's not terribly expensive and will work fine. They also sell octal tube sockets and both Sovtek and Chinese GZ43/5AR4 rectifier tubes.

I would of thought that too, but a friend of mine has a late 63 super reverb his ser no. is A00633 mine is A00109.Mine has the original caps in it ,all astros. and there all in the same direction. Not the 2nd one reversed like all other super reverbs. I think this anp is a proto-type. Whats the earliest super reverb you`ve seen. Keith

I have seen brown Fender Concert amps set up this way from the factory. These were the predecessor to the Super Reverb. So maybe yours is just a carry over using the last of the Concert parts? One way to hazard a guess would be to check if the plate over the rectifier socket hole has the same age discoloration that the chassis has. Also check the sheet metal screws to see if they are the same as used elsewhere on the chassis.

Where are the high voltage supply diodes mounted? Are they on a circuit card like the Bassman's,along with the bias supply components?What's the date code on the power transformer?You should be able to tell if it's factory or not.A repair or mod done at a later date should be noticeable.

Does the transformer have two yellow leads that are not hooked up? I have seen Fender amps wired for solid state rectification, but the transformer had 5volt taps for the tube rectifier. If your amp does have the yellow wires, you could add a tube rectifier(5U4) or leave it solid state. Or get aggressive and have both and install a switch to switch back and forth. Make sure the mp is off when you switch.